Norovirus, which is a single-stranded, positive strand RNA virus belonging to the family calciviridae, causes over 90% of non-bacterial epidemic gastroenteritis worldwide. However, norovirus has been poorly understood because of a lack of a cell culture system supporting norovirus replication (Atmar, R. L. and Estes, M. K., Clinical Microbiology Reviews 14: 15-37, 2001). Norovirus, including human forms of norovirus (i.e., Norwalk virus), can be detected in diagnostic or clinical samples such as stool specimens or vomitus of diseased individuals. Norovirus can also be present in body tissues, such as brain tissue, in an infected mammalian organism. Previous attempts to culture norovirus have been unsuccessful (reviewed in Duizer E, et al. J Gen Virol. 85(Pt 1): 79-87, 2004). There is thus a need to establish a norovirus culture system.